"This sort of thing may be tolerated by the French, but we're British - thank God."

So decreed Field Marshal Montgomery as he urged the House of Lords not to legalise gay sex and warned that the 1967 homosexuality bill would be a "charter for buggery".

More than 30 years on, the gay age of consent has been equalised to 16, homosexuals are allowed to serve in the military - and Britain's most famous wartime general has been outed as a repressed homosexual who had "quasi love affairs" with boys and men, according to a new book.

The Full Monty, by his official biographer, Nigel Hamilton, claims that Montgomery felt passionately about fellow soldiers and boys, some not yet in their teens.

Professor Hamilton, whose official life of Montgomery was in 1981 awarded the Whitbread prize for biography, has drawn on hundreds of letters to and from Montgomery. He admits there was no proof of any physical relationship with any of the young men who wrote, but argues that any act would have been illegal and could have spelt ruin for the wartime hero.

"Don't forget homosexuality was outlawed from 1885 to 1967. Those who did act on their instincts could, like Oscar Wilde, be imprisoned and ruined," he said yesterday from Boston, where he works at the University of Massachusetts.

"He acted very negatively to the change in the law - calling it a 'charter for buggery'. He was extremely worried by it, and psychologically that suggests the law had been an essential crutch in his struggle with his own homosexual feelings."

Rumours about the sexuality of the man who won the battle of El Alamein in 1942, turning the tide of the war in north Africa, have previously circulated.

As early as 1976 - five years after his death - one earlier biographer, Lord Chalfont, noted his "predilection for the company of young men".

Last night, Montgomery's only son, Viscount David Montgomery, dismissed the new claim as being "absurd, appalling, and complete psychobabble".

Another biographer, Alistair Horne, author of The Lonely Leader, commented: "This sounds to me like Hamilton is rehashing his old work for a tabloid readership.

"I served under Montgomery in the Middle East and I have absolutely no evidence whatsoever of repressed, or any other kind, of homosexuality."

Prof Hamilton, who was befriended by the field marshal at age 11 and knew him well for the last 20 years of his life, has no doubt of the nature of Monty's feelings.

"These were quasi love affairs. He became really passionately involved with these young men - and then, more and more, boys, who he would call 'my sons'. They were nothing of the kind, of course, but in his own personality he would frame them in this way.

"I myself have more than 100 very loving letters from him. My relationship with him wasn't sexual, in the sense that it wasn't acted upon, but I had been through enough years at British boarding schools to know what kind of enormous affection and feeling he had for me.

"And I wasn't alone, this was a consistent pattern in Monty's life." One boy was Lucien Treub, Montgomery's "little Swiss friend", who met him at 12, and told Hamilton how the general would bathe him personally and rub him down so he would not catch cold. "I've interviewed him several times and he was quite clear he didn't feel there was any molesting going on, but it's a tricky area," Prof Hamilton said.

Born in 1887, Montgomery was married for 10 years from 1927, but the academic described this an "an aberration" in what had otherwise been a life devoted entirely to being with men.

He added that he had pondered on whether to write about Monty's sexuality when his acclaimed three-part biography was published in the 1980s, but felt that his main aim was to restore the field marshal's military reputation "at a time it was being systematically trashed: I didn't want to detract from that".

Sexuality under scrutiny

Historical figures whose sexuality has been the subject of debate:

TE Lawrence

The soldier and writer claimed, in The Seven Pillars of Wisdom, that he was whipped and raped by a Turkish officer in the first world war. In 1992 his biographer Lawrence James described it as a "homoerotic fantasy", but said Lawrence was homosexual in his later years.

Jane Austen

In 1996 an incestuous relationship was suggested by Terry Castle of Stanford University: the novelist's letters showed "the passionate nature of the sibling bond". She never married, and shared a bed with her sister - but that was not unusual at the time. Austen scholars dismissed the claim.

Daphne du Maurier

Married and a mother of three, the novelist had an affair with the actress Gertrude Lawrence, an authorised biography said in 1993. She had her first fling with a teacher nicknamed "Ferdy", and was torn between "Cairo", or heterosexuality, and "Venice", or lesbianism.

William Shakespeare

Ever since Oscar Wilde claimed the Elizabethan playwright was in love with a boy actor, Willie Hewes, critics have claimed he was gay - relying on his sonnets for justification.

Leonardo da Vinci

The ultimate renaissance man has long been held to be gay ,and in 1476 he was tried and acquitted of sodomy. In 1998, an academic suggested bisexuality in Leonardo's "intense relationship" with a courtesan in his 60s.